Add primary=true for internal storage

Recent patches require this to be set, instead of being determined
automatically.  It should have been set in the first place.

Change-Id: Id33f0c2f8683e44f8c6a4e0193181ab0bb191fef
Merge branch 'cm-10.1' of https://github.com/CyanogenMod/android_device_samsung_n80xx-common into phablet